1. Field of the Invention
This invention relates to a method for the manufacture of fruit wines in which crude fruit juices are concentrated by a semipermeable membrane separation process before fermentation and aging.
2. Description of the Prior Art
Generally, in Japan fruit juices of about 9 to 20 percent sugar content, and in the United States as well as in European countries fruit juices of about 18 to 34 percent sugar content, are used for making fruit wines. As is well known, however, fruit juices having about 20 to 40 percent sugar content are most desirable for making fruit wines.
When fruit juices, whose sugar content is 20 percent and below, are used for making fruit wines, in one conventional method the juices are not concentrated, but rather invert sugar is added to such juices before fermentation or alcohol is added to fruit wines made from such juices after fermentation. Alternatively the juices are concentrated either by the evaporation process or by the freezing process which involve applying special temperatures that may alter the properties of the fruit juices.
To concentrate or not to concentrate fruit juices: that is not the question in the least, because the consensus is that these conventional methods, as long as they use fruit juices of low sugar content, fail to produce fruit wines which must be remarkably distinguished in taste and aroma.
In terms of fermentation temperature, for instance, in producing white wines by the conventional methods, yeast is added to grape juice at 15.degree.C, and the juice is fermented at 20.degree.C and below. It is important that the fermentation temperature, once set at 20.degree.C and below, should be controlled not to fluctuate. Otherwise, white wines of delicate aroma cannot be produced, as is described in Food Industry and Microorganismus by Koichi Yamada, published by Korin Shobo, Japan, 1965, page 221.
With respect to the time period required for making fruit wines by the conventional methods, it takes about 3 to 4 weeks to ferment fruit juices at about 15.degree.C, and 1 to 5 years to age such fruit wines. Generally, a total of about 3 years is necessary to produce high quality fruit wines possessing desired taste and aroma.